1. Field of the Invention
The present invention relates to a method of upgrading low-grade oils, and it relates particularly to a method of recovering refined oils usable as fuel oil from low-grade contaminated oils by directly subjecting said low-grade oils to thermal cracking with a fluidized bed without resorting to any preliminary treatment.
The term `low-grade oils` used herein means oils of low quality containing appreciable amounts of water and/or sludge, and which are definitely unusable as fuel oil as they are. To give typical examples of such oils, there are named waste oils such as used motor oil discharged from gas stations and autorepair shops, lubricating, cutting, cooling and miscellaneous oils discharged from foundries, machine shops and steel mills and the like, and waste oils from petrochemical factories, etc. The term `low grade oil`, as used herein, does not include crude oil as extracted from the earth or any refined fractions thereof. The low grade oils used in this invention contain appreciable amounts of contaminants, usually in amounts of at least 5 weight percent or more. The contaminants usually include water and/or various sludge-forming materials, including metal particles, dirt, various additives conventionally incorporated in oils to improve the properties thereof as well as various undefined materials such as low grade polymers that form in oils during use thereof. Thus, the `low grade oil` consists of spent or waste oil products, i.e., oil products which previously have been used for various purposes or which are generated by various industrial processes, and which are no longer usable for their original intended purposes or in the industrial process concerned, because of excessive contamination and/or high viscosity thereof.
2. Description of the Prior Art
The greater part of the waste oils discharged from such various places of business as above have so far been disposed of by incineration. But, in the light of the disadvantage that the disposal of waste oils by incineration generates soot, smoke and other public nuisances, there have recently been proposed several processes for recovering fuel oil and the like from such waste oils by chemically treating the waste oils. However, all of the processes proposed heretofore require complicated pretreatment processes for separating water and/or sludge from the waste oils to begin with, and yet they fail to recover high-grade oils in amounts proportional to the complexity of the process, so that they are not always satisfactory from the viewpoint of the economics of the process. Meanwhile, the amount of waste oils is likely to increase in the future. Such being the case, development of a method suitable for recovering fuel oils from low grade oils, such as waste oil, by economically refining them without creating public nuisances is eagerly desired.